Archaeological evaluation before or after determination
Evaluating before determination costs money before permission exists. Deferring it to a condition moves the risk to the point where delay costs most. How to choose.
Archaeological evaluation happens either before the council decides your application or afterwards under a condition, and the choice is rarely yours alone. National policy sets the default: where a site includes or has the potential to include heritage assets with archaeological interest, the authority should require a desk-based assessment and, where necessary, a field evaluation. The phrase "where necessary" is where the argument lives.
The local authority's archaeological adviser, usually a county archaeologist or a shared service working from the Historic Environment Record, makes the recommendation. Their view, in practice, decides which route you take.
Why the timing question arises at all
A condition cannot be used to defer information the decision maker needs to decide the application. If the extent and significance of buried remains determine whether the development is acceptable, or determine its layout, that information has to be in front of the committee or the officer at the point of decision.
Where significance is already understood well enough to design mitigation, a condition securing a written scheme of investigation is the proportionate answer. The line between those two situations is a judgement, which is why the same site can attract different advice from different advisers, and why the conversation is worth having early.
What a pre-determination evaluation involves
Evaluation is a staged process, and each stage informs whether the next is needed.
- An archaeological desk-based assessment collating the Historic Environment Record, historic mapping, aerial photography, geological data, previous investigations and the site's land use history, concluding on potential by period.
- Non-intrusive survey where the ground suits it, typically geophysical survey, which covers large areas quickly but performs poorly on some geologies and on made ground.
- Intrusive evaluation, normally trial trenching to a sample of the site area agreed with the adviser, carried out under a written scheme of investigation approved in advance.
- A report setting out what was found, its significance, and the implications for the scheme.
Trial trenching samples are agreed as a percentage of the developable area, and the layout of trenches is designed to test the anomalies and the blank areas rather than only the promising ones. Work has to follow the relevant professional standards, and the adviser will expect the contractor to be appropriately accredited.
Access and programme are the practical constraints. Trenching needs a machine, a competent supervising archaeologist, reinstatement, and ground that is workable, so a winter evaluation on heavy clay can be slower than the same work in spring.
When a council will insist on it
The recurring situations are reasonably predictable.
Where the site lies within an area of known archaeological importance, such as a designated archaeological priority area, or immediately adjacent to a scheduled monument. Where the desk-based assessment identifies high potential for remains of more than local importance. Where the scheme involves deep foundations, basements or extensive ground reduction that would remove any deposits entirely. Where the site is large and greenfield, so that layout could be adjusted to preserve remains in place. And where the proposal is outline, since the layout is not yet fixed and evaluation can shape it.
Conversely, a condition is more likely to be accepted on a small infill site within an existing settlement, on previously developed land with known truncation, or where the footprint is modest and the significance of any remains is likely to be local.
Risks of leaving evaluation to a condition
The attraction of the condition route is obvious: permission first, cost later, and no delay to the decision. The risks are real and fall entirely on the developer.
The most serious is discovery of remains of national importance after permission is granted. Preservation in situ then becomes the policy answer, which can mean redesigning foundations, relocating buildings, or in the worst case finding that a substantial part of the site cannot be built on. A permission does not carry an entitlement to destroy archaeology of that importance.
The second is programme. Excavation triggered by a condition happens after the design is fixed and usually just before construction, precisely when delay costs the most. Post-excavation analysis, specialist reporting and archive deposition then run for months after the fieldwork finishes, and the condition normally requires them.
The third is scope. A written scheme of investigation agreed after permission is negotiated from a weaker position, because the alternative to agreement is a condition that cannot be discharged.
Cost and programme compared
Pre-determination evaluation costs money before you know whether permission will be granted, which is the argument against it. Set against that, it converts an unknown liability into a known one before the land transaction completes, before the design is fixed, and before the contractor is appointed.
For a site with real potential, the comparison usually favours evaluating early. The evaluation result either supports a scheme designed around what is there, or it establishes that little survives, which removes an objection and often removes the condition as well. Where the evaluation finds substantial remains, discovering that at option stage is far better than discovering it after exchange.
The honest uncertainty is that evaluation is a sample. Trial trenching covering a small percentage of a site can miss features, and a negative evaluation does not guarantee clean groundworks. Advisers know this, and a condition for a watching brief often follows even a negative result.
Negotiating the position with the county archaeologist
Approach the adviser before the application, with the desk-based assessment in hand rather than as a question in the abstract. The conversation goes better when there is something to discuss.
Points worth raising:
- The depth and extent of existing truncation, evidenced with borehole logs or a site investigation rather than asserted.
- The foundation solution, and whether a piled design with a suspended slab could preserve deposits in situ.
- The scope for adjusting the layout to keep open space over the sensitive area.
- A staged approach in which geophysical survey precedes any decision on trenching.
Get the outcome in writing. An email confirming that evaluation by condition is acceptable, and on what basis, is worth having when the application is validated and again when the condition is drafted.
What happens when significant remains are found late
If substantial remains appear during excavation under a condition, the immediate step is to stop work in that area and notify the archaeological adviser. Work under the written scheme of investigation then usually moves to full excavation, with the scope revised.
Where the remains may be of national importance, Historic England may be involved and, in rare cases, scheduling can be considered, which changes the legal position entirely. Works affecting a scheduled monument need scheduled monument consent under the Ancient Monuments and Archaeological Areas Act 1979, separately from planning permission.
Practical steps for the developer at that point: keep the contractor informed in writing, record the delay and its cause, review whether a layout change could avoid the area, and talk to the local authority early rather than presenting a completed problem. Where the scheme also carries ecological obligations, sequencing matters, because an excavation area and a habitat creation area can be in competition on the same ground.
An archaeological field evaluation and the reporting that follows should be carried out by a suitably qualified and accredited archaeologist, and councils expect the work to follow recognised professional standards. An AI-assisted draft of the supporting statement is a starting point for that specialist rather than a substitute.
PlanScope drafts desk-based assessments and heritage documents structured to UK planning policy, with site-specific records flagged for your archaeologist to confirm. Enter your postcode to see which reports your site needs. Reports should be reviewed before submission, and we do not guarantee planning approval.
Frequently asked questions
When is pre-determination archaeological evaluation required?
Where the extent and significance of buried remains would affect whether the development is acceptable or how it should be laid out, because a condition cannot defer information the decision maker needs. In practice that means sites in areas of known importance, sites next to scheduled monuments, large greenfield sites and outline applications where layout is not yet fixed.
What does a field evaluation involve?
Usually a staged process: a desk-based assessment collating the Historic Environment Record, historic mapping and previous investigations; non-intrusive survey such as geophysics where the geology suits it; then trial trenching to a sample of the developable area under a written scheme of investigation agreed in advance; and a report on significance and implications.
What are the risks of leaving archaeology to a condition?
Remains of national importance may be found after permission, when preservation in situ can force redesign of foundations or loss of developable area. Excavation triggered by a condition also lands just before construction, when delay is most expensive, and the written scheme of investigation is negotiated from a weaker position.
Does a negative evaluation remove the risk?
Not entirely. Trial trenching samples a percentage of the site, so features can be missed, and advisers often still recommend a watching brief condition after a negative result. The evaluation reduces uncertainty and supports the application, but it does not guarantee that groundworks will be free of archaeological requirements.
Who decides whether evaluation is needed?
The local planning authority, advised by its archaeological adviser, usually a county archaeologist or a shared service working from the Historic Environment Record. Their recommendation generally determines the route, so approach them before submission with a desk-based assessment rather than asking the question in the abstract.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.